The invention relates to an arrangement for controlling an aspect ratio of a video display.
Video sources such as digital versatile disk (DVD), high definition television (HDTV), standard television, and the like, can supply a video signal having an aspect ratio format (source aspect ratio) selected from a range of formats. For example, a 4:3 aspect ratio format and a 16:9 aspect ratio format are supported in consumer products. In modern televisions, the display screen dimensions may be have either a 4:3 or a 16:9 aspect ratio (physical aspect ratio). The viewer may choose to view an image produced from the incoming video signal having dimensions defining an image aspect ratio format that is better adapted to fit the physical aspect ratio of the display screen.
Many consumer electronics devices will allow a user to select the display of source material in an image aspect ratio format that differs from the physical aspect ratio of the display screen. However, such selection, disadvantageously, allows the user to change the aspect ratio in a manner to produce a distorted image.
For example, a consumer may be watching a movie that has a 16:9 source aspect ratio as shown in FIG. 1. Reference 100 represents the image content of a video source material having a 16:9 source aspect ratio. If, as shown in FIG. 2, the user has a 4:3, equal to b/a, physical aspect ratio display device, the user may decide to watch the video in letterbox format to fit the 16:9 program onto the 4:3 display. As such, the top and bottom of the screen are cropped (regions 202, 204) to enable the 16:9 source aspect ratio programming to be shown on the 4:3 physical aspect ratio display device. The resulting image aspect ratio format is 16:9. This provides an acceptable image until the incoming signal changes, perhaps as a result of switching to a commercial that has a 4:3 source aspect ratio, or of changing channels to a source program with a 4:3 source aspect ratio, as shown in FIG. 3. As shown in FIG. 4, the 4:3 source aspect ratio programming is distorted when displayed on a display device having a physical aspect ratio 4:3 that is set to display a 16:9 source aspect ratio program in an image having a 16:9 (d/c) image aspect ratio format.
Some televisions have circuitry that automatically adjusts the aspect ratio that is displayed to match the aspect ratio of the received signal. Such automatic circuits are disclosed in U.S. Pat. Nos. 5,949,494; 5,146,331; 5,323,235; and 5,343,238. However, these aspect ratio control circuits, disadvantageously, do not enable the user to control the aspect ratio that is displayed.
In carrying an inventive feature, a user can select an aspect ratio for the image according to the user preference. However, when a change in the aspect ratio of the source material is detected that could result in a distortion, the image aspect ratio format is automatically changed to insure that an undistorted picture is generated. Thereby, the arrangement automatically overrides the user""s selection, for example, only when necessary to avoid a distorted picture.
A video display apparatus, embodying an inventive feature includes a source of a video, first signal. A detector is provided for generating a second signal identifying an aspect ratio format of the video signal. A source of a control, third signal indicative of a preferred, first image aspect ratio format is provided. A display controller is responsive to the first, second and third signals for producing, on a display screen, an image having the first image aspect ratio format, selected in accodance with the third signal, when the video signal has a first video signal format. The display controller changes automatically the first image aspect ratio of the image to a different image aspect ratio format, in accordance with the second signal, in a manner to override the first signal, when a format of the video signal changes to a second video signal format.